Film flotation



Aug. 18, 1942. E. J. MAUsT ET'AL FILM FLOTATION Filed Dec. 27, 1939 INYEXTORS /Vhql/S 7',

po g

ATTORNEY.

Patented Aug. 18, 1942 UNITED STATES PATENT OFFICE FILM, FLoTA'rIoN Ernest J. Maust and Clinton A. Hollingsworth,

Brewster, Fla., assignors to American Cyan amid Company, New York, N. Y., a corporation of Maine 4Application December 27, 1939, serial No. 311,093

2: claims. (c1. 209-297) The present invention relates to improved apparatus and process for the concentration or separation of ore materials by film flotation.

One of the `well-known processes of recovering values from ore materials is by the adoption of the film flotation principle in which the surface tension of water is taken advantage of to selectively float certain ore constituents while other ore constituents not supported by the surface film. sink. The concentrating of ore materials by lm flotation is most frequently employed for concentrating ore materialsv of a relatively coarse size range, for example the process is usually adopted to effect a classification of ore materials ranging in size from a minus mesh to about a plus 28 mesh. Ore materials falling within this size range represent a rather coarse or awkward fraction which cannot be profitably concentrated by the ordinary flotation methods or in which the reagent costwould be too high for froth fiotation.

According to the present invention an improved apparatus and process is provided for delm flotation of phosphate rock or silica in the phosphate industry and it can be applied to various other material, for example concentrationof iron ore, cleaning of coal, the classification of cement rock, bauxite, graphite, feldspar, kyanite, barytes chromite, and also the various metallic ore materials.

The improved apparatus and process of the present invention is particularly well suited for the concentration VVof the B. P. L. values from phosphate rock in which the particles are coarser than 28 mesh. 'I'his coarse fraction of phosphate rock cannot profitably be concentrated by froth flotation. When attempting to concentrate by froth flotation, if enough reagents are added to effectively float these coarse particles, usually the nest portion of the gangue is also oated, and

, thus a low grade concentrate is produced. When Y the finer particles are separated from the coarse particles and the coarse fraction is subjected to a froth flotation treatment, an excessively large` amount of reagent is required. Even with the" excessive and expensive amount of reagent used on this coarse fraction in frothv flotation, it is still diiiicult to obtain satisfactory recovery, since in the absence of the ner particles it is very diflicult to maintain a stable froth. f

Itis an advantage of the preferred embodiment of the present invention, therefore, that the B. P. L. values from the coarser fractions of phosphate rock are obtained in higher yields of improved grade and with a lower reagent cost than by froth flotation methods.

The'improve'd film iiotation machine ofthe present invention also offers advantages over other methods of lm flotation such as concentrating tables, vanners, etc., in that the initial cost is lower, less oor space, operating attention,

with the surface of the separating medium, to

gently deposit the 'particlesupon the surface of said separating medium, whereupon certain particles are supported by the surface iilm and may be separated from those particles which are not supported by the surface lm, and hence sink. The ore materials prior to deposition on the perforated roll or belt may be treated with various reagents to render some of the ore constituents more readily oatable than other ore constituents and in this manner effecting a preferential lm of one or more of the ore constituents. For

example, in the recovery of the values from phosphate rock, the material if treated with a reagent mixture of fatty acid, fuel oil and caustic soda will result in the phosphate particles 'being floated.

while the silica sinks, or if treated with a cationic wetting agent will result in the silica being more readily floatable than the phosphate particles.

The improved apparatus of the present invention illustrated by the following drawing in,

Fig. 1 is a top plan view of the improved apparatus partly in section;

Fig. 2 is a vertical sectional view taken along the line 2-2 of Fig l; and

Fig. 3 is a view similar to Fig. 2 on an enlarged scale showing a portion thereof.

In the drawing like reference numerals indicate corresponding parts in the different gures.

A retaining tank I which is preferably of the construction shown, namely, of a general triangular shape from the side view, and supported by a suitable framework I8, and a perforated roll or cylinder 2 is shown positioned in' the upper portion of the tank underneath a feed hopper 3. The retaining tank hasva water inlet I1 located behind a shield 9 and on the opposite side an overow lip or adjustable overflow Weir 6. A baiiie 'l is shown positioned in the retaining tank intermediate the perforated drum or cylinder 2 and the adjustable overow weir 6 in such a manner that water must pass through the perforated :roll in order to reach the overflow 6. The bottom of the retaining tank is normally closed by a valve I held in position by a weight II acting upon a pivot I2. per 3 is shown mounted above the perforated roll 2 and has a rubber guard 5 and an adjustable rubber feed lip 4. The rubber guard and the adjustable' feed lip 4 are positioned with respect to the perforated roll 2 in such a manner that rotation of the roll results in ore materials contained in the feed hopper being deposited or fed onto the roll in a layer approximately one particle thick. Referring now particularly to Fig. l, the perforated roll is shown mounted on a shaft I3, rotatably mounted on the retainingv tank I by-means of the bearings I6. A sprocket drive wheel I4 is shown mounted on one end of the shaft I3 which is adapted to be driven by means of a sprocketchain from a suitable source of power (not shown).

In utilizing the improved apparatus for concentrating ore materials the ore material preferably ground to approximately minus l0 to plus 28 mesh is placed in the feed hopper 3.. The perforated roll 2 is rotated by means of the sprocket I4 and shaft I3, whereupon a thin layer of the ore particles is deposited upon the upper surface of the perforated cylinder; The perforations of the cylinder are of a size that substantially none of the solids pass through them but through which water flows freely. Water is fed into the retaining tank behind the shield 9 and flows toward the overiiow lip 6 whereupon the baiiie 1 causes the water to pass through the perforated roll. As the solid particles oln the perforate'droll reach the point I9, water passing through the roll contacts the solid particles at this point and gently deposits the particles upon the surface of the water, 'whereupon certain of the ore constituents which are readily wettable sink and are collected as the tailings 8 in the bottom of the retaining tank. The ore constituents that are not readily wettable are supported y by the surface film and are carried over the I cles.

overflow lip 6 and may. be collected by any suitable method. 'Ihe particles that sink to the bottom of the retainingI tank are collected as shown at 8 until the weight of such particles is sufficient to overcome the effect if the weight II to open the discharge valve Il), the arm of which is pivoted at I2. Material is discharged untilthe weight I I again closes the valve. Water may conveniently be added to the feed by means of a spray I5 located about. the feed hopper.

One of the important features of this improved apparatus is the manner in which the adjustable rubber feed lip 4 operates to .'deposit a uniform layer of approximately one particle thick upon the surface of the perforated cylinder. It is readily seen that if the material is fed onto the perforated roll in too thick a. stream or layer,

and thence onto the surface of the separating medium, the particles that one wishes to'sink are carried mechanically over with the particles one wishes to float'. In orderto obtain the full capacity of the apparatus the entire length -of the feed roll along the surface should be covered at all times with a one-particle layer of the partl- The adjustable rubber feed lip can be regulatedy to produce this desired effect much more efficiently than an ordinary fixed or rigid feed opening.

The feed hop- Vfeed hopper.

Another advantage of the rubber feed lip is' thatstray particles, coarserv than the opening between the lip and the perforated roll when present in the feed do not clog the opening. With a rigid lip these stray coarse particles would accumulate and clog the small opening, that has to be maintained, which would result in a loss of production and possible damage to the machine. With the adjustable rubber feed lip the opening lbetween the lip and the perforated roll can easily be adjusted to deposit a layer of the desired thickness onto the perforated roll and ,when a stray coarse particle comes along, it

pauses a moment at the lip, and then due to friction contact with the roll and other particles the rubber lip flips open and the coarse particle is discharged. Without the rubber lip the machine would require constant operating attention with possible failure in operation, Whereas with the rubber lip it operates with very little attention to insure 7the most efficient and desirable results.

The relationship of the rubber lip and the perforated roll are such that in spite of the small opening lthe capacity of the apparatus compares favorably with machines of the prior art. The capacity of the small opening is compensated for by the speed at which the roll operates. The speed is variable and can be adjusted to obtain the maximum recovery from a particular ore and without danger of the machine clogging orchok- Another operating feature is the use of a small amount of water with the feed. The feed is more evenly and properly distributed on the roll when a small amount of water is added to the 'I'he amount of water to be added l will vary with different materials and the spray regulation of the amount of water that passes y through the perforated r'oll. When a high grade concentrate is wanted, the rate of water flow is reduced, thus giving the gangue more time to drop out. When the speed of the roll is increased or decreased, the character of the feed, or the reagents altered, the water flow can be regulated to produce the maximum recovery under the altered conditions.

The following examples illustrate the operativeness of the present invention when utilized in concentrating phosphate rock.

EXAMPLE 1 A phosphate rock feed of -10 mesh with about 15% passing through 20 mesh was conditioned with a reagent mixture of a fatty acid, fuel oil, and caustic soda and subjected to a film flotation operation utilizing the improved apparatus of the present invention. The results were as follows:

Ffoating -phosphate B. P. L.

Recovery Exnrru: 2

A second sample of the phosphate rock described in Example 1 was pretreated. with a cationic wetting agent to render the phosphate .more readily wettable than the silica, and the silica was floated using the improved apparatus Vof the present invention. The results of the silica flotation are as follows:

Floating silica The grade and recoveries in the above examples were not only good but the reagent cost and conto, and may be employed to concentrate any ore material, whether metallic or non-metallic.

We claim:

1. A nlm flotation apparatus comprising a liquid retaining tank having an overflow lip and means for introducing water into said tank, a horizontally rotatable perforated cylinder positioned in the upper central portion of the tank and parallel to the overflow lip, said cylinder being partially immersed in water when the retaining tank is nlled to overflowing, a feed hopper located above the perforated cylinder, said cylinder forming the bottom of the hopper, and having an adjustable flexible feed lip engaging the cylinder for depositing solid materials in a thin layer upon the upper surface of the perforated cylinder, a bafiie extending from a point below the water level immediately adjacent the perforated cylinder causing water flowing toward the overflow lip of the tank to pass through said perforated member and-co-acting with the overflow lip to create a zone in the tank in which there is no upward current of water.

2. A nlm flotation apparatus comprising a liquid retaining tank having a water inlet on one side and an overflow lip on the opposite side, a horizontally rotatable perforated` cylinder positioned in the upper central portion of the tank,

and parallel to the overflow lip, said cylinder being partially immersed in water when the retaining tank is filled to overowing, a feed hopper located above the perforated cylinder, said cylinder forming the bottom of the hopper, and having an adjustable rubber feed lip engaging the cylinder for depositing solid particles in a thin layer upon the upper surface of said perforated cylinder, and a baille extending from a point below the water level immediately adjacent the perforated cylinder causing water nowing toward the overflow lip of the tank to pass through said perforated member and co-acting with the overflow lip to create a zone in the tank in which there is no upward current of water.

` ERNEST J. MAUST.

CLINTON A. HOLLINGSWOR. 

